Conventionally, a lens barrel telescopically adjustable in its whole length in a direction of optical axis is in practical and widespread use. Such a lens barrel can be expanded and contracted between an imaging standby position, in which the lens barrel expands forward from its applied camera body, and a retracted position, in which the lens barrel is shortened than the imaging standby position and stored in the camera body.
In such an extensible lens barrel, under the retracted position, part of lens group of an imaging optical system generally retracts from the imaging light path. (For example, refer to JP2008170650A.)
Recently, electronic imaging devices acquiring electronically still and moving images, such as digital cameras, are also widely spread, which comprise imaging elements, such as CCD (Charge Coupled Device) and the like, for receiving optical images (subject images) formed by an imaging optical system and photo-electrically converting them into image data. Moreover, such an electronic imaging device, has been proposed, that comprises an image blur compensating device for compensating image blur resulting from camera shake by displacing the imaging elements within a plane parallel to a light receiving plane (for example, JP2008048220A).
As disclosed in JP2008170650A, it should have a group of retraction lenses with small apertures, which are located nearby an aperture diaphragm in the imaging position if part of the lens group of the imaging optical system should be retracted from the imaging light path, for saving a retraction space, and then reducing a size of the lens barrel in a radial direction thereof.
However, in a retracted position, each lens of the groups located around the retraction lenses in the imaging standby position usually approaches each other due to shortening of the lens barrel. Moreover, these lenses are located relatively far from the aperture diaphragm in the imaging standby position, so that these lenses generally have larger apertures than those of retraction lens group, and the more parting far from the retraction lenses, the larger lens aperture is. Thus, if a lens group on the object side relative to the retraction lens group includes two lenses in the imaging standby position, one of the lenses on the object side will have larger aperture than the other lens on the imaging side.
If the retracting space for the retraction lens group is configured to allow at least a part of a lens with largest aperture among those lenses located nearby the retraction lenses in the imaging standby position, to be present in the space in the radial direction, the size of the lens barrel in the radial direction will become larger, and as a result, it will be concerned that a camera body comprising such a lens barrel will also become larger.
In addition, in the lens barrel disclosed in JP2008170650A, the image side end of the retraction lenses in the retracted position are more extending toward the imaging element than the image side end of the lens group located nearby the imaging elements in the imaging standby position.
Therefore, the lens barrel disclosed in JP2008170650A is not easily applied to an electronic imaging device comprising an image blur compensating device, such as a device disclosed in JP2008048220A, because a lens frame for the retaining retraction lens group and a retracting mechanism for the retraction lens group and the like interfere with the image blur compensating device in the retracted position.